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-rw-r--r--lib/radix-tree.c92
1 files changed, 92 insertions, 0 deletions
diff --git a/lib/radix-tree.c b/lib/radix-tree.c
index 348eaefbed7..a2f9da59c19 100644
--- a/lib/radix-tree.c
+++ b/lib/radix-tree.c
@@ -1203,6 +1203,98 @@ radix_tree_gang_lookup_tag_slot(struct radix_tree_root *root, void ***results,
}
EXPORT_SYMBOL(radix_tree_gang_lookup_tag_slot);
+#if defined(CONFIG_SHMEM) && defined(CONFIG_SWAP)
+#include <linux/sched.h> /* for cond_resched() */
+
+/*
+ * This linear search is at present only useful to shmem_unuse_inode().
+ */
+static unsigned long __locate(struct radix_tree_node *slot, void *item,
+ unsigned long index, unsigned long *found_index)
+{
+ unsigned int shift, height;
+ unsigned long i;
+
+ height = slot->height;
+ shift = (height-1) * RADIX_TREE_MAP_SHIFT;
+
+ for ( ; height > 1; height--) {
+ i = (index >> shift) & RADIX_TREE_MAP_MASK;
+ for (;;) {
+ if (slot->slots[i] != NULL)
+ break;
+ index &= ~((1UL << shift) - 1);
+ index += 1UL << shift;
+ if (index == 0)
+ goto out; /* 32-bit wraparound */
+ i++;
+ if (i == RADIX_TREE_MAP_SIZE)
+ goto out;
+ }
+
+ shift -= RADIX_TREE_MAP_SHIFT;
+ slot = rcu_dereference_raw(slot->slots[i]);
+ if (slot == NULL)
+ goto out;
+ }
+
+ /* Bottom level: check items */
+ for (i = 0; i < RADIX_TREE_MAP_SIZE; i++) {
+ if (slot->slots[i] == item) {
+ *found_index = index + i;
+ index = 0;
+ goto out;
+ }
+ }
+ index += RADIX_TREE_MAP_SIZE;
+out:
+ return index;
+}
+
+/**
+ * radix_tree_locate_item - search through radix tree for item
+ * @root: radix tree root
+ * @item: item to be found
+ *
+ * Returns index where item was found, or -1 if not found.
+ * Caller must hold no lock (since this time-consuming function needs
+ * to be preemptible), and must check afterwards if item is still there.
+ */
+unsigned long radix_tree_locate_item(struct radix_tree_root *root, void *item)
+{
+ struct radix_tree_node *node;
+ unsigned long max_index;
+ unsigned long cur_index = 0;
+ unsigned long found_index = -1;
+
+ do {
+ rcu_read_lock();
+ node = rcu_dereference_raw(root->rnode);
+ if (!radix_tree_is_indirect_ptr(node)) {
+ rcu_read_unlock();
+ if (node == item)
+ found_index = 0;
+ break;
+ }
+
+ node = indirect_to_ptr(node);
+ max_index = radix_tree_maxindex(node->height);
+ if (cur_index > max_index)
+ break;
+
+ cur_index = __locate(node, item, cur_index, &found_index);
+ rcu_read_unlock();
+ cond_resched();
+ } while (cur_index != 0 && cur_index <= max_index);
+
+ return found_index;
+}
+#else
+unsigned long radix_tree_locate_item(struct radix_tree_root *root, void *item)
+{
+ return -1;
+}
+#endif /* CONFIG_SHMEM && CONFIG_SWAP */
/**
* radix_tree_shrink - shrink height of a radix tree to minimal